Inflator with dynamic pressure compensation

ABSTRACT

A method of inflating a vehicle tire, having an internal volume between about 10 gallons and about 12 gallons, includes discharging compressed air into the internal volume with an inflator. The inflator has an inflator housing, a motor within the inflator housing defining a motor axis and including an output shaft rotatable about the motor axis, a DC power source configured to provide power to the motor at a nominal output voltage, and a pump within the inflator housing and coupled to the output shaft. The pump includes a cylinder defining a cylinder axis and a piston that is reciprocable within the cylinder along the cylinder axis in response to rotation of the output shaft. By discharging compressed air into the internal volume, increasing a static pressure of the internal volume by 5 pounds per square inch (psi) from a starting pressure in the internal volume between 28 psi and 31 psi occurs within 40 to 60 seconds.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 17/207,018, filed on Mar. 19, 2021, which is a continuation ofU.S. patent application Ser. No. 16/280,689, filed on Feb. 20, 2019, nowU.S. Pat. No. 10,974,701, which claims the benefit of Chinese PatentApplication No. 201810169213.5, filed on Feb. 28, 2018, the entirecontents of all of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to inflators.

BACKGROUND OF THE INVENTION

Many objects, such as vehicle tires, bicycle tires, sports balls, floattubes, and the like, must be filled with compressed air. Such objectsmay be filled with air using a variety of different filling devices,such a manual pump, a compressor, or a portable inflator. Typically, auser must monitor the pressure within the object to determine when adesired fill pressure has been reached. The user may monitor thepressure using a separate pressure gauge or a pressure gauge that isincorporated into the filling device.

SUMMARY OF THE INVENTION

The present invention provides, in one aspect, a method of inflating avehicle tire having an internal volume between about 10 gallons andabout 12 gallons. The method includes discharging compressed air intothe internal volume with an inflator. The inflator has an inflatorhousing, a motor within the inflator housing defining a motor axis andincluding an output shaft rotatable about the motor axis, a DC powersource configured to provide power to the motor at a nominal outputvoltage, and a pump within the inflator housing and coupled to theoutput shaft. The pump includes a cylinder defining a cylinder axis anda piston that is reciprocable within the cylinder along the cylinderaxis in response to rotation of the output shaft. By dischargingcompressed air into the internal volume, increasing a static pressure ofthe internal volume by 5 pounds per square inch (psi) from a startingpressure in the internal volume between 28 psi and 31 psi occurs within40 to 60 seconds.

The present invention provides, in another aspect, an inflator includingan inflator housing, a motor within the inflator housing, the motordefining a motor axis and including an output shaft rotatable about themotor axis, a DC power source configured to provide power to the motorat a nominal output voltage, and a pump within the inflator housing andcoupled to the output shaft. The pump includes a cylinder defining acylinder axis and a piston that is reciprocable within the cylinderalong the cylinder axis in response to rotation of the output shaft. Theinflator is operable to discharge compressed air into an internal volumebetween about 10 gallons and about 12 gallons to increase a staticpressure of the internal volume by 5 pounds per square inch (psi) from astarting pressure in the internal volume between 28 psi and 31 psi.Increasing the pressure by 5 psi occurs within 40 to 60 seconds.

Other features and aspects of the invention will become apparent byconsideration of the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an inflator according to one embodimentof the invention.

FIG. 2 is another perspective view of the inflator of FIG. 1.

FIG. 3 is a cross-sectional view of the inflator of FIG. 1.

FIG. 4 is a perspective view of a portion of the inflator of FIG. 1.

FIG. 5 is a cross-sectional view of a control module of the inflator ofFIG. 1.

FIG. 6 illustrates a control system for the inflator of FIG. 1 accordingto an embodiment of the invention.

FIGS. 7A, 7B, and 7C are a process for controlling the operation of theinflator of FIG. 1.

FIGS. 8A, 8B, and 8C are another process for controlling the operationof the inflator of FIG. 1.

FIG. 9A is another process for controlling the operation of the inflatorof FIG. 1.

FIG. 9B is another process for controlling the operation of the inflatorof FIG. 1.

FIGS. 9C, 9D, and 9E are another process for controlling the operationof the inflator of FIG. 1.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways. Also, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

DETAILED DESCRIPTION

FIGS. 1-5 illustrate a portable inflator 10 according to an embodimentof the invention. The inflator 10 includes an inflator housing 14 havinga front side 18, a rear side 22, and left and right sides 26, 30extending between the front side 18 and the rear side 22 (FIG. 1). Theillustrated housing 14 is a clamshell housing defined by cooperatinghalves joined at a parting plane 34 that bisects the inflator 10. Inother embodiments, the parting plane 34 may not bisect the inflator 10.Alternatively, the housing 14 may be a unitary structure, or may beformed in other ways.

In the illustrated embodiment, an external frame 38 is coupled to theoutside of the housing 14. The frame 38 is preferably made from animpact-resistant material (e.g., a polycarbonate-ABS blend), and theframe's placement on the housing 14 may help protect the housing 14 fromfalls or other impacts. The illustrated frame 38 includes a firstportion 42 extending along the left side 26 of the housing 14, a secondportion 46 extending along the right side 30 of the housing 14, and athird portion 50 extending between the first and second portions 42, 46.The third portion 50 defines a handle that is spaced from the housing 14and that can be gripped by a user to facilitate carrying and moving theinflator 10. In the illustrated embodiment, each of the first and secondportions 42, 46 of the frame 38 further includes a base 54 extending ina front-rear direction along the left and right sides 26, 30 of thehousing 14, respectively. Each base 54 includes a plurality of feet 58(FIG. 2) that are engageable with a surface (not shown) when theinflator 10 is set upright (i.e. the orientation illustrated in FIG. 1)upon the surface. The feet 58 are preferably made of a resilientmaterial (e.g., rubber or silicone) to dampen vibrations generatedduring operation of the inflator 10.

The inflator 10 further includes a motor 62 supported within the housing14 (FIG. 3) and a battery 66 (FIG. 1) configured to provide power to themotor 62. The battery 66 is removably coupled to a battery receptacle70, which is located at least partially within a battery recess 74 thatextends inward from the front side 18 of the housing 14. The illustratedbattery 66 is a power tool battery pack with a plurality of rechargeablebattery cells (e.g., lithium-based battery cells; not shown) providingthe battery 66 with a nominal output voltage of about 12V or less. Inother embodiments, the battery 66 can have a different nominal voltage,such as, for example, 18V, 36V, or 40V. Alternatively, the inflator 10may be a corded tool configured to receive power from a wall outlet orother remote power source, such as a lead acid battery.

Referring to FIG. 3, the inflator 10 includes a pump 78 and a driveassembly 82 for providing torque from the motor 62 to the pump 78. Theillustrated motor 62 is a DC electric motor and may be a brushed orbrushless electric motor. The motor 62 includes an output shaft 86defining a motor axis 90. The drive assembly 82 is at least partiallyhoused within a gear case 94 and includes a pinion 98 fixed to theoutput shaft 86 for rotation about the motor axis 90, a bevel gear 102meshed with the pinion 98 and rotatable about a gear axis 104 transverseto the motor axis 90, and a crank arm 106 coupled to the bevel gear 102at an eccentric pivot 110 that is offset from the gear axis 104. Thepump 78 includes a cylinder 114 defining a cylinder axis 118, that istransverse to both the motor axis 90 and the gear axis 104, and a piston122 coupled to the crank arm 106. The piston 122 is reciprocable withinthe cylinder 114 along the cylinder axis 118 in response to rotation ofthe bevel gear 102.

In some embodiments, the cylinder 114 has an internal diameter, D,between about 23 millimeters (mm) and about 29 mm. In the illustratedembodiment, the internal diameter, D, is about 26 mm. In someembodiments, the piston 122 is movable along the cylinder axis 118 astroke length, L, between about 15 mm and about 21 mm. In theillustrated embodiment, the stroke length, L, is about 18 mm.Accordingly, in the illustrated embodiment, the pump 78 has an internalcylinder diameter to stroke length ratio, D:L, of about 1.44.

Based on the internal diameter, D, of the cylinder 114 and the strokelength, L, of the piston 122, the pump 78 has a displacement per stroke,Q_(S), that can be calculated as set forth below in EQN. 1:

Q _(S)=¼D ² ×L×π   EQN. 1

Accordingly, in some embodiments, the pump 78 has a displacement perstroke, Q_(S), between about 6.25 cubic centimeters and about 14 cubiccentimeters. In the illustrated embodiment, the pump 78 has adisplacement per stroke, Q_(S), of about 9.5 cubic centimeters.

In some embodiments, the bevel gear 102 can be driven by the motor 62 upto a maximum speed, N, between about 3500 revolutions per minute (RPM)and about 4500 RPM. In the illustrated embodiment, the bevel gear 102can be driven by the motor 62 up to a maximum speed, N, of about 4000RPM. The flow rate, Q, of the pump 78 can be calculated by multiplyingthe displacement per stroke, Q_(S), by the rotational speed, N, of thebevel gear 102 as set forth below in EQN. 2:

Q=Q _(S) ×N   EQN. 2

Accordingly, in some embodiments, the pump 78 has a flow rate, Q,between about 21,875 cubic centimeters per minute (cc/min) and about63,000 cc/min at a discharge pressure of 0 psig. In some embodiments,the pump 78 has a flow rate, Q, of about 25,000 cc/min (or about 25liters per minute) at a discharge pressure of 0 psig. With the battery66 having a nominal output voltage of about 12V in some embodiments, theinflator 10 can therefore have a flow rate to battery voltage ratio,Q:V, between about 1,822 cc/min per volt and about 5,250 cc/min per voltin some embodiments. For example, the flow rate to battery voltage ratioQ:V may be about 2,083 cc/min per volt. The high flow rate, Q, andcorresponding flow rate to battery voltage ratio Q:V of the inflator 10advantageously allows the inflator 10 to quickly fill inflatable objectsto a desired pressure.

For example, the inflator 10 may be used to fill pneumatic tires forvehicles. A typical tire for a passenger vehicle has an internalfillable volume between about 10 gallons and about 12 gallons. In someembodiments, the inflator 10 can increase the static pressure in a 10-12gallon tire from 28-31 (or about 30) pounds per square inch (psi) to 35psi in between 40 seconds and 60 seconds. In some embodiments, theinflator 10 can increase the static pressure in a 10-12 gallon tire from28-31 pounds per square inch (psi) to 35 psi in between 40 seconds and50 seconds. The inflator 10 was tested on a 245/45R19 vehicle tirehaving an internal volume of about 10.5 gallons. Using a battery with anominal output voltage of 12 V, the inflator 10 filled the tire from astarting pressure of 25 psi to a static pressure of 40 psi in 119seconds.

Referring to FIG. 3, the pump 78 further includes an outlet chamber 126and a one-way valve 130 disposed between the outlet chamber 126 and thecylinder 114. The illustrated valve 130 is a spring-biased poppet valve;however, any other suitable type of one-way valve may be used. The valve130 is configured to open when pressure within the cylinder 114 exceedsa cracking pressure of the valve 130 (e.g., when the piston 122 moves inthe direction of arrow A during its compression stroke). The valve 130is configured to close when the piston 122 moves in the direction ofarrow B during its return stroke so as to maintain an elevated pressurewithin the outlet chamber 126. An inlet opening 134 is providedproximate an end of the cylinder 114 opposite the outlet chamber 126(FIG. 4). The illustrated inlet opening 134 extends radially through thecylinder 114 and allows ambient air to flow into the cylinder 114 (forsubsequent compression) at the end of the piston's return stroke.

With reference to FIGS. 2 and 4, an outlet hose 138 extends from theoutlet chamber 126 and through an opening 142 in the rear side 22 of thehousing 14. The outlet hose 138 terminates at an adapter 146. Theadapter 146 may be connected to an extension hose 150, a variety ofadapters 154, and the like. In the illustrated embodiment, the inflator10 includes a hose wrap 158 with an integrated storage compartment 162coupled to the rear side 22 of the housing 14 for storing the extensionhose 150 and the adapters 154.

A control unit 166 is provided for controlling operation of the inflator10 (FIGS. 4 and 5). The illustrated control unit 166 includes a printedcircuit board 170 (“PCB”) provided with a controller 174 (FIG. 6) and auser interface 178. With reference to FIG. 5, the user interface 178includes a display 200, such as a monochromatic display, a liquidcrystal diode (LCD) display, or other display that is capable ofdisplaying alphanumeric data, and a plurality of keys or buttons 204. Inthe illustrated embodiment, the buttons 204 are coupled to switches 208on the PCB 170. In other embodiments, the display 200 may betouch-sensitive, and one or more of the buttons 204 may be virtualbuttons displayed on the display 200. The user can communicate with thecontroller 174 via the display 200 and/or the buttons 204, which allowthe user to make selections from the display 200, enter data, and thelike. Each button 204 may correspond with different actions shown on thedisplay 200, allowing the user to interact with the controller 174 toturn the inflator 10 on/off, control operation of the inflator 10, etc.

The control unit 166 is disposed generally above the battery 66 andincludes a cover plate 208 extending at an oblique angle relative to thefront side 18 of the housing 14 (FIG. 1). A first seal 212 surrounds thecover plate 208 to provide a substantially water-tight seal between thecover plate 208 and the housing 14 (FIG. 5). In the illustratedembodiment, a lens 216 overlies the display. The lens 216 is preferablymade of a transparent, impact-resistant material such as polycarbonate.A second seal 220 is disposed between the lens 216 and an underside ofthe cover plate 208 to provide a substantially water-tight seal betweenthe lens 216 and the cover plate 208.

Referring to FIGS. 4 and 5, the control unit 166 further includes one ormore pressure sensors 224 in communication with the controller 174. Atube 228 extends from a first fitting 232 on the pressure sensor 224 toa second fitting 236 on the outlet chamber 126. The tube 228 establishesfluid communication between the pressure sensor 224 and the outletchamber 126 such that the pressure sensor 224 can detect the pressurewithin the outlet chamber 126 (and, therefore, the pressure within theobject being inflated).

The power provided by the battery pack 66 to the inflator 10 iscontrolled, monitored, and regulated using control electronics withinthe inflator 10, as illustrated in the electromechanical diagram of FIG.6. FIG. 6 illustrates the controller 174 associated with the inflator10. The controller 174 is electrically and/or communicatively connectedto a variety of modules or components of the inflator 10. For example,the illustrated controller 174 is connected to a power input module 300,a battery pack interface 302, one or more temperature sensors 304, theone or more pressure sensors 224, a user interface module 178, a remotecommunication interface 306, and a motor switching module 308 (e.g.,including one or more switching FETs). The controller 174 includescombinations of hardware and software that are operable to, among otherthings, control the operation of the inflator 10, control the userinterface 178, monitor the operation of the inflator 10, etc.

In some embodiments, the controller 174 includes a plurality ofelectrical and electronic components that provide power, operationalcontrol, and protection to the components and modules within thecontroller 174 and/or the inflator 10. For example, the controller 174includes, among other things, a processing unit 310 (e.g., amicroprocessor, a microcontroller, or another suitable programmabledevice), a memory 312, input units 314, and output units 316. Theprocessing unit 310 includes, among other things, a control unit 318, anarithmetic logic unit (“ALU”) 320, and a plurality of registers 322(shown as a group of registers in FIG. 6), and is implemented using aknown computer architecture, such as a modified Harvard architecture, avon Neumann architecture, etc. The processing unit 310, the memory 312,the input units 314, and the output units 316 as well as the variousmodules connected to the controller 174 are connected by one or morecontrol and/or data buses (e.g., common bus 324). The control and/ordata buses are shown generally in FIG. 6 for illustrative purposes. Theuse of one or more control and/or data buses for the interconnectionbetween and communication among the various modules and components wouldbe known to a person skilled in the art in view of the inventiondescribed herein.

The memory 312 includes, for example, a program storage area and a datastorage area. The program storage area and the data storage area caninclude combinations of different types of memory, such as read-onlymemory (“ROM”), random access memory (“RAM”) (e.g., dynamic RAM[“DRAM”], synchronous DRAM [“SDRAM”], etc.), electrically erasableprogrammable read-only memory (“EEPROM”), flash memory, a hard disk, anSD card, or other suitable magnetic, optical, physical, electronicmemory devices, or other data structures. The processing unit 310 isconnected to the memory 312 and executes software instructions that arecapable of being stored in a RAM of the memory 312 (e.g., duringexecution), a ROM of the memory 312 (e.g., on a generally permanentbasis), or another non-transitory computer readable medium such asanother memory or a disc. Software included in the implementation of theinflator 10 can be stored in the memory 312 of the controller 174. Thesoftware includes, for example, firmware, one or more applications,program data, filters, rules, one or more program modules, and otherexecutable instructions. The controller 174 is configured to retrievefrom memory and execute, among other things, instructions related to thecontrol processes and methods described herein. In other embodiments,the controller 174 may include additional, fewer, or differentcomponents.

The battery pack interface 302 includes a combination of mechanical andelectrical components configured to, and operable for, interfacing(e.g., mechanically, electrically, and communicatively connecting) theinflator 10 with the battery pack 66. For example, power provided by thebattery pack 66 to the inflator 10 is provided through the battery packinterface 302 to the power input module 300. The power input module 300includes combinations of active and passive components to regulate orcontrol the power received from the battery pack 66 prior to power beingprovided to the controller 174. The battery pack interface 302 alsosupplies power to the motor switching module 308 to be switched by theswitching FETs to selectively provide power to the motor 62. The batterypack interface 302 also includes, for example, a communication line 326for providing a communication line or link between the controller 174and the battery pack 66. The remote communication interface 306 (e.g., aBluetooth, NFC, WAN, USB, Ethernet, cellular, mesh network, or similarinterface) enables a user to control the user interface 178 using anexternal or remote device (e.g., a mobile phone or a computer; notshown) via a wired or wireless connection. In some embodiments, theremote communication interface is configured to receive a signal relatedto a target pressure value the inflator 10 is desired to achieve.

FIGS. 7A, 7B, and 7C are a process 400 for controlling the operation ofthe inflator 10. The process 400 begins with the controller 174receiving a pressure sensor signal, P_(SENSOR), from the pressure sensor224 (STEP 402). The controller 174 then determines a raw pressure value(STEP 404). In some embodiments, the raw pressure, P_(RAW), value iscalculated as set forth below in EQN. 3:

P _(RAW) =P _(SENSOR)×Const_Adjust_(A)+Cons_Adjust_(B)   EQN. 3

where Const_Adjust_(A) and Cons_Adjust_(B) are constants stored in thememory 312 that are specific to the pressure sensor 224. These valuesare used to determine raw pressure each time a new pressure value needsto be determined based on a signal from the pressure sensor 224.

At STEP 406, the controller 174 determines whether the inflator 10 iswithin an environment where the temperature is greater than or equal to30° Celsius or another prescribed temperature value. The controller 174determines the temperature associated with the inflator's surroundingenvironment based on a signal received from the temperature sensor 304.No matter the outcome of STEP 406, the controller 174 determines atemperature corrected pressure, P_(TC), from the raw pressure, P_(RAW)(STEP 408, 410). Depending on the temperature of the inflator'senvironment, the temperature corrected pressure, P_(TC), is calculatedusing different temperature offset values. For example, at STEP 408,when the temperature is greater than or equal to 30° Celsius, thetemperature corrected pressure, P_(TC), is calculated to compensate forany increases in pressure due to a temperature greater than or equal to30° Celsius. At STEP 410, when the temperature is less than 30° Celsius,the temperature corrected pressure, P_(TC), is calculated to compensatefor any decreases in pressure due to a temperature lower than 30°Celsius. One skilled in the art would be capable of calculating thetemperature corrected pressure, P_(TC), based on the well-knownrelationship between temperature and pressure and in view of thisdisclosure.

Following the determination of the temperature corrected pressure,P_(TC), the controller 174 determines whether the motor 62 is ON (STEP412). If the motor 62 is ON, the process 400 proceeds to control sectionA shown in and described with respect to FIG. 7B. If the motor 62 isOFF, the process 400 proceeds to control section B shown in anddescribed with respect to FIG. 7C.

With reference to control section A and FIG. 7B, the controller 174determines whether the motor 62 has been ON and working for specifiedduration or time or motor-ON limit (STEP 414). The duration for whichthe motor 62 has been working can be determined based on a timerinternal to the controller 174 and monitoring a motor-ON pin of thecontroller 174. When the motor 62 is turned ON, the motor-ON pin is setto ON and a motor-ON timer begins to run. Similarly, when the motor 62is turned OFF, the motor-ON pin is set to OFF and the motor-ON timer isstopped. As a result, the controller 174 keeps track of how long themotor 62 has been running. If, at STEP 414, the motor 62 has beenworking for the motor-ON limit, the controller 174 stores thetemperature corrected pressure, P_(TC), as a previous pressure value,P_(PREV) (STEP 416). In some embodiments, the motor-ON limit is 4.0seconds. Following STEP 416, the process 400 returns to control sectionC shown in and described with respect to FIG. 7A so the process 400 canbegin again. In some embodiments, the process 400 is executed every 0.4seconds. If, at STEP 414, the motor 62 has not been working for themotor-ON limit, the controller 174 determines whether the motor 62 hasbeen working for longer than the motor-ON limit (STEP 418). If, at STEP418, the motor 62 has not been working for longer than the motor-ONlimit, the process 400 returns to control section C and FIG. 7A so theprocess 400 can begin again. If, at STEP 418, the motor 62 has beenworking for longer than the motor-ON limit, the controller 174determines a motor delay time, T_(MD) (STEP 420).

The motor delay time, T_(MD), corresponds to the amount of time that themotor is to be operated before a pressurization condition of theinflator 10 is terminated. The motor delay time, T_(MD), is calculatedbased on a rate of pressurization change for sensed pressure, R_(PC),and a static pressure, P_(STATIC), associated with the tube 228 before apressurization condition of the inflator 10 is initiated (describedbelow). The rate of pressurization change, R_(PC), is calculated as setforth below in EQN. 4:

$\begin{matrix}{R_{PC} = \frac{P_{TC} - P_{PREV}}{Limit}} & {{EQN}.\mspace{14mu} 4}\end{matrix}$

where P_(TC) is the temperature corrected pressure value from STEP 408or STEP 410, and P_(PREV) is the previous pressure value from STEP 416.In some embodiments, the rate of pressurization change, R_(PC), isaveraged over several iterations of its calculation. For example, therate of pressurization can be calculated with each iteration of theprocess 400 (e.g., every 0.4 seconds) or each time the motor-ON limit isreached (e.g., every four seconds). No matter the interval, thecontroller 174 can average multiple calculations of the rate ofpressurization change, R_(PC). By averaging the rate of pressurizationchange, R_(PC), the controller can limit large rate fluctuations thatcan result from anomalous sensor readings.

A static pressure value, P_(STATIC), is then calculated. The staticpressure value, P_(STATIC), is regularly being updated throughout apressurization condition of the inflator 10. The static pressure value,P_(STATIC), is initially determined before the motor 62 is turned on.However, after the pressurization condition has begun, the staticpressure value is updated by adding the rate of pressurization, R_(PC),multiplied by the motor-ON limit (i.e., P_(TC)-P_(PREV)). Accordingly,the controller 174 effectively adds a delta pressure value, ΔP,corresponding to the amount of pressure added during the most recentmotor-ON time interval. With the static pressure value, P_(STATIC), andthe rate of pressurization change, R_(PC), the controller 174 calculatesthe motor delay time, T_(MD), as set forth below in EQN. 5:

$\begin{matrix}{T_{MD} = \frac{( {P_{{TARGE}T} - P_{S{TATIC}}} )}{R_{PC}}} & {{EQN}.\mspace{14mu} 5}\end{matrix}$

where P_(TARGET) is a target pressure value set using the user interface178. The motor delay time, T_(MD), has units of seconds and graduallyapproaches zero as the pressurization condition of the inflator 10progresses. After the motor delay time, T_(MD), is calculated at STEP420, the motor-ON timer described above can be reset to zero to begincounting for the next motor-ON time interval.

Following STEP 420, the controller 174 determines whether the motordelay time, T_(MD), is less than or equal to zero (STEP 422). At thepoint when the motor delay time, T_(MD), reaches zero or substantiallyzero (e.g., an arbitrarily close number to zero), the updated staticpressure, P_(STATIC), substantially equals the target pressure,P_(TARGET). If, at STEP 422, the motor delay time, T_(MD), is not equalto or less than zero, the process 400 returns to control section C shownin and described with respect to FIG. 7A so the process 400 can beginagain. If, at STEP 422, the motor delay time, T_(MD), is equal to orless than zero, the process 400 proceeds to STEP 424 where thecontroller 174 turns OFF the motor 62 and terminates the pressurizationcondition of the inflator 10 in response to the updated static pressure,P_(STATIC), equaling the target pressure, P_(TARGET). Following STEP424, the process 400 returns to control section C shown in and describedwith respect to FIG. 7A so the process 400 can begin again.

Returning to STEP 412 and FIG. 7A, if the motor 62 is OFF, the process400 proceeds to control section B shown in and described with respect toFIG. 7C. With reference to FIG. 7C, the static pressure value,P_(STATIC), is set to the temperature compensated pressure, P_(TC) (STEP426). At STEP 428, the controller 174 determines if the motor is OFF.When the motor 62 is turned OFF, a motor-OFF pin is set to OFF. However,if the motor is not OFF (i.e., the motor has begun working), thecontroller 174 sets a current pressure value equal to the temperaturecompensated pressure, P_(TC) (STEP 430). After the current pressure isset at STEP 430, the process 400 returns to control section C shown inand described with respect to FIG. 7A so the process 400 can beginagain. If, at STEP 428, the motor 62 is OFF, a motor-OFF timer begins torun and is incremented at STEP 432. At STEP 434, the motor-OFF timer iscompared to a motor-OFF limit (e.g., 1.25 s). If, at STEP 434, themotor-OFF timer is greater than or equal to the motor-OFF limit, thecontroller 174 sets a current pressure value equal to the temperaturecompensated pressure, P_(TC), and resets the motor-OFF bit to reset themotor-OFF timer (STEP 436). After the current pressure is set at STEP436, the process 400 returns to control section C shown in and describedwith respect to FIG. 7A so the process 400 can begin again.

Returning to STEP 434, if the motor-OFF timer is not greater than orequal to the motor-OFF limit, the controller 174 sets the currentpressure value equal to the user desired target pressure, P_(TARGET),received from the user interface 178 (STEP 438). After the currentpressure is set at STEP 438, the process 400 returns to control sectionC shown in and described with respect to FIG. 7A so the process 400 canbegin again.

FIGS. 8A, 8B, and 8C are another process 500 for controlling theoperation of the inflator 10. The process 500 differs from the process400 in that control of the inflator is based on a battery pack voltageadjusted pressure value. The process 500 begins with the controller 174receiving a pressure sensor signal, P_(SENSOR), from the pressure sensor224 (STEP 502). The controller 174 then determines a raw pressure value(STEP 504). In some embodiments, the raw pressure, P_(RAW), value iscalculated as set forth below in EQN. 6:

P _(RAW) =P _(SENSOR)×Const_Adjust_(A)+Cons_Adjust_(B)   EQN. 6

where Const_Adjust_(A) and Cons_Adjust_(B) are constants stored in thememory 312 that are specific to the pressure sensor 224. These valuesare used to determine raw pressure each time a new pressure value needsto be determined based on a signal from the pressure sensor 224.

At STEP 506, the controller 174 determines whether the inflator 10 iswithin an environment where the temperature is greater than or equal to30° Celsius or another prescribed temperature value. The controller 174determines the temperature of the inflator's surrounding environmentbased on a signal received from the temperature sensor 304. No matterthe outcome of STEP 506, the controller 174 determines a temperaturecorrected pressure, P_(TC), from the raw pressure, P_(RAW) (STEP 508,510). Depending on the temperature of the inflator's environment, thetemperature corrected pressure, P_(TC), is calculated using differenttemperature offset values. For example, at STEP 508, when thetemperature is greater than or equal to 30° Celsius, the temperaturecorrected pressure, P_(TC), is calculated to compensate for anyincreases in pressure due to a temperature greater than or equal to 30°Celsius. At STEP 510, when the temperature is less than 30° Celsius, thetemperature corrected pressure, P_(TC), is calculated to compensate forany decreases in pressure due to a temperature lower than 30° Celsius.One skilled in the art would be capable of calculating the temperaturecorrected pressure, P_(TC), based on the well-known relationship betweentemperature and pressure.

Following the determination of the temperature corrected pressure,P_(TC), the controller 174 determines whether the motor 62 is ON (STEP512). If the motor 62 is ON, the process 500 proceeds to control sectionD shown in and described with respect to FIG. 8B. If the motor 62 isOFF, the process 500 proceeds to control section E shown in anddescribed with respect to FIG. 8C.

With reference to control section D and FIG. 8B, the controller 174determines a voltage adjusted pressure value, P_(VA) (STEP 514). Thevoltage adjusted pressure value, P_(VA), is determined as a function ofthe voltage of the battery pack 66. In some embodiments, the voltageadjusted pressure value, P_(VA), can be calculated for any measuredvoltage of the battery pack 66. In other embodiments, the voltageadjusted pressure value, P_(VA), is only calculated for a couplediscrete voltage values (e.g., 12V and 10V) corresponding generally to“high” voltages and “low” voltages.

As an illustrative example, the temperature compensated pressure,P_(TC), can be adjusted based on a 10V battery pack voltage and a 12Vbattery pack voltage. A 10V pressure value and a 12V pressure value canbe calculated for the adjustment as set forth below in EQNS. 7 and 8:

P _(10V) =P _(TC)×Adjust_Gassing_(10A)+Adjust_Gassing_(10B)   EQN. 7

P _(12V) =P _(TC)×Adjust_Gassing_(12A)+Adjust_Gassing_(12B)   EQN. 8

where Adjust_Gassing_(10A), Adjust_Gassing_(10B), Adjust_Gassing_(12A),Adjust_Gassing_(12B) are constant values stored in the memory 312related to how pressurization from the inflator 10 changes with respectto the voltage level of the battery pack 66. Generally speaking, thecloser a battery pack voltage is to a nominal voltage for the batterypack 66, the closer to unity (i.e., 1) a constant scaler multiplier forvoltage-based pressure adjustment will be. The voltage adjusted pressurevalue, P_(VA), can then be calculated as set forth below in EQN. 9:

$\begin{matrix}{P_{VA} = {\frac{( {P_{10V} - P_{12V}} ) \times ( {V_{BP} - {12V}} )}{( {{10V} - {12V}} )} + P_{12V}}} & {{EQN}.\mspace{14mu} 9}\end{matrix}$

Following STEP 514, the controller 174 determines whether the voltageadjusted pressure value, P_(VA), is greater than or equal to the userdesired target pressure, P_(TARGET) (STEP 516). If, at STEP 516, thevoltage adjusted pressure value, P_(VA), is not greater than or equal tothe user desired target pressure, P_(TARGET), the process 500 returns tocontrol section F shown in and described with respect to FIG. 8A so theprocess 500 can begin again. If, at STEP 516, the voltage adjustedpressure value, P_(VA), is greater than or equal to the user desiredtarget pressure, P_(TARGET), the process 500 proceeds to STEP 518 wherethe controller 174 turns off the motor 62 and terminates thepressurization condition of the inflator 10. Following STEP 518, theprocess 500 returns to control section F shown in and described withrespect to FIG. 8A so the process 500 can begin again.

Returning to STEP 512 and FIG. 8A, if the motor 62 is off, the process500 proceeds to control section E shown in and described with respect toFIG. 8C. With reference to FIG. 8C, the static pressure value,P_(STATIC), is set to the temperature compensated pressure, P_(TC) (STEP520). At STEP 522, the controller 174 determines if the motor 62 is OFF.When the motor 62 is turned OFF, a motor-OFF pin is set to OFF. However,if the motor 62 is not OFF (i.e., the motor 62 has begun working), thecontroller 174 sets a current pressure value equal to the temperaturecompensated pressure, P_(TC) (STEP 524). After the current pressure isset at STEP 524, the process 500 returns to control section F shown inand described with respect to FIG. 8A so the process 500 can beginagain. If, at STEP 522, the motor 62 is OFF, a motor-OFF timer begins torun and is incremented at STEP 526. At STEP 528, the motor-OFF timer iscompared to a motor-OFF limit (e.g., 1.25 s). If, at STEP 528, themotor-OFF timer is greater than or equal to the motor-OFF limit, thecontroller 174 sets a current pressure value equal to the temperaturecompensated pressure, P_(TC), and resets the motor-OFF bit to reset themotor-OFF timer (STEP 530). After the current pressure is set at STEP530, the process 500 returns to control section F shown in and describedwith respect to FIG. 8A so the process 500 can begin again.

Returning to STEP 528, if the motor-OFF timer is not greater than orequal to the motor-OFF limit, the controller 174 sets the currentpressure value equal to the user desired target pressure, P_(TARGET),received from the user interface 178 (STEP 532). After the currentpressure is set at STEP 532, the process 500 returns to control sectionF shown in and described with respect to FIG. 8A so the process 500 canbegin again. In some embodiments, the voltage adjusted pressuretechnique of the process 500 can be included in and combined with themotor delay time technique of the process 400 such that measuredpressure values can be adjusted for the voltage of the battery pack 66.

FIGS. 9A, 9B, 9C, and 9D provide another control methodology forcontrolling the operation of the inflator 10. The control methodology ofFIGS. 9A, 9B, 9C, and 9D is divided into three discrete processes thatcan be executed by the controller 174 independently, sequentially, orsimultaneously. FIG. 9A is a process 600 for controlling the ON/OFFoperation of the motor 62 after an inflate button of the user interface178 is pressed by a user. FIG. 9B is a process 700 for determiningwhether the inflator 10 can continue to be operated based on temperaturefault conditions and battery pack voltage fault conditions. FIGS. 9C and9D are a process for controlling the termination of a pressurizationcondition of the inflator 10.

With reference to FIG. 9A and the process 600, the process 600 beginswith the controller 174 determining whether an inflate button of theuser interface 178 has been pressed by a user (STEP 602). If the inflatebutton has not been pressed, the process 600 will return to STEP 602until the inflate button of the user interface 178 is pressed. If, atSTEP 602, the inflate button has been pressed, the controller 174determines whether the motor 62 is OFF (STEP 604). If the motor is notOFF (i.e., motor is ON), the controller 174 turns OFF the motor 62 (STEP606) and the process 600 returns to STEP 602. After returning to STEP602, it is not necessary that a user press the inflate button a secondtime. For example, if the inflate button has been pressed within apredetermined time interval (e.g., within 5 seconds), the controller 174can consider the inflate button to have been pressed and the controller174 again checks to see if the motor 62 is OFF at STEP 604.

If, at STEP 604, the motor 62 is OFF, the controller 174 determines atemperature of the inflator 10 to determine whether the temperature isoutside of an acceptable operational temperature range (e.g., greaterthan predetermined temperature value such as 50° C.). In someembodiments, the controller 174 determines the temperature of theinflator 10's surrounding environment based on a signal received fromthe temperature sensor 304. If the temperature of the inflator 10 is notwithin an acceptable operational temperature range, the process 600ends. After the process 600 ends, the process 600 can again be executedimmediately or following a delay (e.g., 2 seconds) to again check to seeif the temperature of the inflator is within an acceptable operationaltemperature range. If, at STEP 608, the temperature of the inflator iswithin an acceptable operational temperature range, the controller 174determines whether the target pressure set by a user is greater than asensed pressure by the pressure sensor 224 (STEP 610). If the targetpressure is not greater than the sensed pressure, there is no need toinflate an object and the process 600 ends. If, at STEP 610, the targetpressure is greater than the sensed pressure, the controller 174 turnson the motor 62 (STEP 612) to initiate a pressurization condition of theinflator 10 and then the process 600 ends. In some embodiments, if auser has not provided a target pressure value at STEP 610, thecontroller 174 sets a target pressure value to a predetermined value(e.g., 120 pounds per square inch [“PSI”]).

With reference to FIG. 9B and the process 700, the process 700 beginswith the controller 174 determining whether the motor 62 is ON (STEP702). If the motor 62 is not ON (i.e., motor is OFF), the process 700returns to STEP 702 and the controller 174 waits for the motor 62 to beturned ON. If, at STEP 702, the motor 62 is ON, the controller 174determines a temperature of the inflator 10 to determine whether thetemperature is outside of an acceptable operational temperature range(e.g., greater than predetermined temperature value such as 50° C.)(STEP 704). In some embodiments, the controller 174 determines thetemperature of the inflator 10's surrounding environment based on asignal received from the temperature sensor 304. If the temperature ofthe inflator 10 is not within an acceptable operational temperaturerange, the controller 174 turns OFF the motor 62 (STEP 708). If, at STEP704, the temperature of the inflator is within an acceptable operationaltemperature range, the controller 174 determines whether the voltage ofthe battery pack 66 is within an acceptable range (i.e., less than ahigh-voltage cutoff value and greater than a low-voltage cutoff value)(STEP 706). For example, certain types of battery cells used in batterypacks, such as lithium-based battery cells, have prescribed upper andlower voltage cutoff values. If the battery cell or battery pack 62'svoltage reaches an upper voltage limit during charging, charging can bediscontinued. Alternatively, if the battery cells or battery pack 62reach a low-voltage limit during use, the controller 174 can preventfurther discharge of the battery cells or battery pack 62. If, at STEP706, the battery pack voltage is not within an acceptable range, thecontroller 174 turns OFF the motor 62 (STEP 708). If the battery pack62's voltage is within an acceptable range, the process 700 ends. Afterthe process 700 ends, the process 700 can again be executed immediatelyor following a delay (e.g., 2 seconds) to again check to see if thetemperature of the inflator and the voltage of the battery pack 62 arewithin acceptable operational ranges.

With reference to FIGS. 9C and 9D and the process 800, the process 800begins with the controller 174 determining whether the motor 62 is ON(STEP 802). If the motor 62 is not ON (i.e., motor is OFF), the process800 returns to STEP 802 and the controller 174 waits for the motor 62 tobe turned ON. If, at STEP 802, the motor 62 is ON, the controller 174determines whether a user has adjusted the target pressure to a newvalue (STEP 804). If a user adjusted the target pressure to a new value,the controller 174 will reset a motor working time variable (e.g., howlong the motor 62 has been ON) (STEP 806). The controller 174 may alsoreset a FIRST TIME bit if a sensed pressure has previously exceededtarget pressure value (described below). The process 800 then returns toSTEP 802. If, at STEP 804, the user has not adjusted the target pressureto a new value, the controller 174 determines whether sensed pressure isgreater than or equal to an upper pressure limit (e.g., 120 PSI) (STEP808). If the sensed pressure is greater than or equal to the upperpressure limit, the controller 174 turns OFF the motor 62 (STEP 810) andthe process 800 ends. If, at STEP 808, the sensed pressure is less thanthe upper pressure limit, the controller 174 increments a TIMER (STEP812). The TIMER can be used to terminate a pressurization condition ofthe inflator 10. The process 800 then proceeds to control section Jshown in and described with respect to FIG. 9D.

With reference to FIG. 9D and control section J of the process 800, thecontroller 174 determines whether the motor working time has reached afirst limit (e.g., 4 seconds) (STEP 814). If, at STEP 814, the motorworking time has not reached the first limit, the controller 174determines a pressure difference, ΔP, between the target pressure valueand a current sensed pressure value (STEP 816). After the controller 174determines the pressure difference at STEP 816, the process 800 returnsto control section K and FIG. 9C where the process 800 ends before beingre-executed. In some embodiments, the process 800 is executed once every0.4 seconds.

If, at STEP 814, the motor working time has reached the first limit, thecontroller 174 determines whether the motor working time has reached asecond limit (e.g., 12 seconds) (STEP 818). If the motor working timehas not reached the second limit, the controller 174 determines a motordelay time, T_(MD) (STEP 820). The motor delay time, T_(MD), correspondsto the amount of time that the motor 62 is to be operated before apressurization condition of the inflator 10 is terminated. The motordelay time, T_(MD), is calculated based on a rate of pressurizationchange for sensed pressure, R_(PC), and a delta pressure value, ΔP,between the target pressure value and the current sensed pressure value.The rate of pressurization change, R_(PC), is calculated as set forthbelow in EQN. 10:

$\begin{matrix}{R_{PC} = \frac{P_{S} - P_{SPREV}}{INTERVAL}} & {{EQN}.\mspace{14mu} 10}\end{matrix}$

where P_(S) is the current sensed pressure value, P_(SPREV) is theprevious sensed pressure value from the previous iteration of theprocess 800, and INTERVAL is the interval of time between P_(S) andP_(SPREV) (e.g., 0.4 seconds, 4.0 seconds, etc.). In some embodiments,the rate of pressurization change, R_(PC), is averaged over severaliterations of its calculation. For example, the rate of pressurizationcan be calculated with every iteration of the process 800 (e.g., 0.4second interval) or each time the motor working time reaches the firstlimit (e.g., 4 second interval). No matter the interval, the controller174 can average multiple calculations of the rate of pressurizationchange, R_(PC). By averaging the rate of pressurization change, R_(PC),the controller can limit large rate fluctuations that can result fromanomalous sensor readings. The motor time delay, T_(MD), is determinedby dividing the delta pressure value, ΔP, between the target pressurevalue and the current sensed pressure value by the rate ofpressurization change, R_(PC), as shown below in EQN. 11.

$\begin{matrix}{T_{MD} = \frac{\Delta P}{R_{PC}}} & {{EQN}.\mspace{14mu} 11}\end{matrix}$

After the controller 174 determines the motor delay time, T_(MD), thecontroller 174 compares the value of the TIMER to the determined motordelay time, T_(MD) (STEP 822). If the motor delay time, T_(MD), is lessthan or equal to the TIMER, the controller 174 turns OFF the motor (STEP838). If the motor delay time, T_(MD), is greater than the TIMER, theprocess 800 returns to control section K and FIG. 9C where the process800 ends before being re-executed.

Returning to STEP 818, if the motor working time has reached the secondlimit, the controller 174 determines whether the current sensed pressureis less than the target pressure value (STEP 824). In some embodiments,the current sensed pressure is compared to a value less than a user-settarget pressure. For example, the current sensed pressure can becompared to the user-set target pressure minus a preset value (e.g.,minus a value between 0.1 PSI and 5.0 PSI). If, at STEP 824, the sensedpressure is less than the target pressure, the motor working time isreset to zero and the process 800 returns to control section K and FIG.9C where the process 800 ends before being re-executed. If, at STEP 824,the current sensed pressure is greater than or equal to the targetpressure, the controller 174 determines whether the current sensedpressure is greater than or equal to the target pressure for the firsttime (STEP 828). If the current sensed pressure is greater than or equalto the target pressure for the first time, the process 800 proceeds tocontrol section M shown in and described with respect to FIG. 9E.

If, at STEP 828, the current sensed pressure is greater than or equal tothe target pressure for a second or subsequent iteration of the process800, the controller 800 decrements the motor delay time (STEP 830).After decrementing the motor delay time, T_(MD), the controller 174compares the value of the motor delay time, T_(MD), to zero (STEP 832).If the motor delay time, T_(MD), is less than or equal to zero, thecontroller 174 turns OFF the motor (STEP 834) and the process 800returns to control section K and FIG. 9C where the process 800 ends. Ifthe motor delay time, T_(MD), is greater than zero, the process 800returns to control section J and STEP 814.

With reference to control section M and FIG. 9E, the controller 174 hasdetermined that the current sensed pressure was greater than or equal tothe target pressure for the first time. The controller 174 then sets aFIRST TIME BIT to indicate that this is the first instance of thecurrent sensed pressure being greater than or equal to the targetpressure (STEP 836). Following STEP 836, the controller 174 determines atarget sensor pressure (STEP 838). The target sensor pressure differsfrom the user-set target pressure because it is compensated for a dropoff value related to the voltage of the battery pack 66. The drop offvalue compensates the user-set target pressure based on the reducedeffectiveness of the battery pack 66 to power the inflator as itsvoltage decreases. As battery pack voltage decreases, the inflator 10does not provide pressurized air at the same rate as when the batterypack 66 is fully-charged. Additionally, the higher the target PSI for anobject being inflated, the more quickly the battery pack 66's voltage isdepleted. For example, the battery pack voltage drop off value can beempirically predetermined based on the user-set target pressure and acurrent voltage of the battery pack 66. Depending upon the currentvoltage of the battery pack 66 (e.g., 12V, 10V, etc.) and the user-settarget pressure, the controller 174 retrieves the predetermined drop offvalue from the memory 312 for compensating the user-set target pressure.Generally, the lower the battery pack 66's voltage and the higher theuser-set target pressure, the greater the battery pack voltage drop offvalue.

After the target sensor pressure is determined at STEP 838, thecontroller 174 determines a new motor delay time, T_(MD) (STEP 840). Themotor delay time, T_(MD), corresponds to the amount of time that themotor 62 is to be operated before a pressurization condition of theinflator 10 is terminated. The controller 174 terminates apressurization condition when the motor time delay, T_(MD), equals zero(i.e., has been successively decremented to a value less than or equalto zero). The motor delay time, T_(MD), is calculated as set forth abovein EQN. 11. After the controller 174 determines the motor delay time,T_(MD), the controller 174 determines whether the motor time delay,T_(MD), is greater than or equal to a time limit (e.g., approximately100 seconds) (STEP 842). If, at STEP 842, the motor time delay, T_(MD),is greater than or equal to the time limit, the controller 174 sets themotor time delay, T_(MD), to the value of the time limit (STEP 844).Following STEP 844, the controller 174 determines whether the motor timedelay, T_(MD), is less than or equal to zero (STEP 846). If the motortime delay, T_(MD), is less than or equal to zero, the controller 174turns OFF the motor (STEP 848) and the process 800 returns to controlsection K and FIG. 9C where the process 800 ends. If, at STEP 842, themotor time delay, T_(MD), is less than the time limit, the controller174 determines whether the motor time delay, T_(MD), is less than orequal to zero (STEP 846). If the motor time delay, T_(MD), is less thanor equal to zero, the controller 174 turns OFF the motor (STEP 848) andthe process 800 returns to control section K and FIG. 9C where theprocess 800 ends. If, at STEP 846, the motor time delay, T_(MD), isgreater than zero, the process 800 returns to control section J and STEP814.

Various features and advantages of the invention are set forth in thefollowing claims.

What is claimed is:
 1. A method of inflating a vehicle tire having aninternal volume between about 10 gallons and about 12 gallons, themethod comprising: discharging compressed air into the internal volumewith an inflator, the inflator including an inflator housing, a motorwithin the inflator housing, the motor defining a motor axis andincluding an output shaft rotatable about the motor axis, a DC powersource configured to provide power to the motor at a nominal outputvoltage, and a pump within the inflator housing and coupled to theoutput shaft, the pump including a cylinder defining a cylinder axis anda piston that is reciprocable within the cylinder along the cylinderaxis in response to rotation of the output shaft; and by dischargingcompressed air into the internal volume, increasing a static pressure ofthe internal volume by 5 pounds per square inch (psi) from a startingpressure in the internal volume between 28 psi and 31 psi, whereinincreasing the pressure by 5 psi occurs within 40 to 60 seconds.
 2. Themethod of claim 1, wherein increasing the pressure by about 5 psi occurswithin 50 to 60 seconds.
 3. The method of claim 1, wherein the nominaloutput voltage is 12V or less.
 4. The method of claim 1, wherein the DCpower source is a battery pack removably coupleable to the inflatorhousing.
 5. The method of claim 4, wherein the inflator housing includesa recess in a front side of the inflator housing, and wherein thebattery pack is at least partially disposed within the recess when thebattery pack is coupled to the inflator housing.
 6. The method of claim1, wherein the motor axis is transverse to the cylinder axis.
 7. Themethod of claim 6, further comprising a drive assembly configured tocouple the motor to the pump, the drive assembly including a pinionfixed to the output shaft, a bevel gear meshed with the pinion, and acrank arm extending between the bevel gear and the piston, the crank armconfigured to reciprocate the piston in response to rotation of thebevel gear.
 8. The method of claim 7, wherein the bevel gear isrotatable about a gear axis that is transverse to the motor axis and thecylinder axis.
 9. The method of claim 1, wherein the pump has adisplacement per stroke between 6 cubic centimeters and 14 cubiccentimeters.
 10. The method of claim 1, wherein the pump has a maximumflow rate between about 21,875 cubic centimeters per minute (cc/min) andabout 63,000 cc/min.
 11. An inflator comprising: an inflator housing; amotor within the inflator housing, the motor defining a motor axis andincluding an output shaft rotatable about the motor axis; a DC powersource configured to provide power to the motor at a nominal outputvoltage; and a pump within the inflator housing and coupled to theoutput shaft, the pump including a cylinder defining a cylinder axis anda piston that is reciprocable within the cylinder along the cylinderaxis in response to rotation of the output shaft; wherein the inflatoris operable to discharge compressed air into an internal volume betweenabout 10 gallons and about 12 gallons to increase a static pressure ofthe internal volume by 5 pounds per square inch (psi) from a startingpressure in the internal volume between 28 psi and 31 psi, and whereinincreasing the pressure by 5 psi occurs within 40 to 60 seconds.
 12. Theinflator of claim 11, wherein increasing the pressure by about 5 psioccurs within 50 to 60 seconds.
 13. The inflator of claim 11, whereinthe nominal output voltage is 12V or less.
 14. The inflator of claim 11,wherein the DC power source is a battery pack removably coupleable tothe inflator housing.
 15. The inflator of claim 14, wherein the inflatorhousing includes a recess in a front side of the inflator housing, andwherein the battery pack is at least partially disposed within therecess when the battery pack is coupled to the inflator housing.
 16. Theinflator of claim 11, wherein the motor axis is transverse to thecylinder axis.
 17. The inflator of claim 16, further comprising a driveassembly configured to couple the motor to the pump, the drive assemblyincluding a pinion fixed to the output shaft, a bevel gear meshed withthe pinion, and a crank arm extending between the bevel gear and thepiston, the crank arm configured to reciprocate the piston in responseto rotation of the bevel gear.
 18. The inflator of claim 17, wherein thebevel gear is rotatable about a gear axis that is transverse to themotor axis and the cylinder axis.
 19. The inflator of claim 11, whereinthe pump has a displacement per stroke between 6 cubic centimeters and14 cubic centimeters.
 20. The inflator of claim 11, wherein the pump hasa maximum flow rate between about 21,875 cubic centimeters per minute(cc/min) and about 63,000 cc/min.